Hydraulic excavators are very versatile machines and are readily adaptable to be fitted with one of many different types of hydraulically actuated work implements such as a conventional bucket, a hydraulic hammer, a shear, a grapple, and so forth. One of the problems encountered by the hydraulic excavator manufacturer is that each of the different types of work implements has different hydraulic requirements. For example, the operating position of a bucket is normally manually controlled and requires very precise metering of fluid flow to and from the hydraulic cylinder connected to the bucket for precise positioning of the bucket relative to the stick. On the other hand, a shear is normally hydraulically powered to the open or closed positions very quickly with only minimal or no metering of fluid flow to the shear actuator. A hydraulic hammer is normally driven continuously for some period of time such that the hydraulic requirement generally requires a fairly constant fluid flow with minimal operator intervention other than starting and stopping the hammer.
Thus, it is desirable to provide a hydraulic system readily adjustable to provide the hydraulic requirements for a variety of work implements and a control logic therefor to readily alter control of the hydraulic system to match the work implement requirements.